Method for the surface treatment of an article

ABSTRACT

A method for the surface treatment of an article (2) by means of a robotic device (3) comprising a robotic arm (5) and a spraying head (4) fitted on the robotic arm (5); the method comprises a learning step, during which the operator moves the spraying head (4) by means of a handling device (9) and the movements made by the spraying head (4) are stored by a storage unit (8); and a reproduction step, which is subsequent to the learning step and during which the robotic arm (5) is operated so that the spraying head (4) repeats the movements stored by the storage unit (8).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. Nationalization of PCT Application NumberPCT/IB2017/055972, filed on Sep. 28, 2017, which claims priority to ITPatent Application No. 102016000097482 filed on Sep. 28, 2016, theentireties of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention concerns a method and a plant for the surfacetreatment of an article.

The present invention is advantageously applied in the field ofenamelling of ceramic articles, to which the following descriptionexplicitly refers without loss of generality.

CONTEXT OF THE INVENTION

In the field of the working of ceramic articles, robotic devices areknown to be used supporting spraying heads for painting and/orenamelling the surfaces.

This type of approach has a high versatility and effectiveness and hasled to an increase in production speed and improvements in repeatabilityand precision of the industrial process.

In view of the fact that the same robot can paint and/or enamel articlesof different shapes, the way in which it is “taught” how to act hasbecome an increasingly important work step and should be as simple andintuitive as possible.

Currently, the most widely used teaching techniques are: point to pointprogramming (PTP), off-line programming and programming byself-learning.

In point to point programming, the operator moves the robot from pointto point, carrying out the movements which it will then replicate withthe help of a control system (e.g. a control panel). However, thisapproach has several drawbacks including the following: to program therobot, the robot itself has to be used (thus resulting in productiondowntime) and programming is fairly laborious (the robot has to be movedto each point of the path and its position has to be saved); and inorder to evaluate the result, the program must be completed and thenrun; if the result is not satisfactory, these operations must berepeated.

In off-line programming, the various actions of the robot are planned ona remote computer using a programming language and then sent to therobot.

The off-line and PTP programming methods are complex and laborious andthis makes them particularly inefficient for the production of small andmedium-sized batches.

Teaching techniques based on self-learning are simpler and moreintuitive since they do not require knowledge of the robot programminglanguage. However, in these cases, the programming phase requires theuse of a robot suited to the programming method. The robot (complex andcostly to produce) must be provided with appropriate mechanical,pneumatic or hydraulic balancing systems which allow the operator tocarry out the self-learning programming with limited effort, relievingthe operator as far as possible of the load due to the weight andinertia of the moving parts of the robot. In any case, the operatorsustains a significant physical effort, which can make it difficult forhim/her to impose precise movements on the robot.

The object of the present invention is to provide a method and a plantfor the surface treatment of an article, which overcome, at leastpartially, the drawbacks of the known art and are, at the same time,easy and inexpensive to produce.

SUMMARY

According to the present invention, a method and a plant are providedfor surface treatment according to the following independent claims and,preferably, in any one of the claims depending directly or indirectly onthe independent claims.

In this text, by “torque” we mean “moment of a force” or in any caseanother quantity containing (more precisely, a function of) the momentof a force. “Moment of a force” (or “mechanical moment”) has the commonmeaning of the aptitude of a force to impart a rotation to a rigid bodyaround a point (in a plane) or an axis (in space) when said force is notapplied to the centre of mass.

In this text, by “force” we also mean (in addition to the meaningnormally given to this term) another quantity containing (moreprecisely, a function of) the force. According to some embodiments,“force” means force according to its normal meaning.

BRIEF DESCRIPTION OF THE FIGURES

The invention is described below with reference to the accompanyingdrawings, which illustrate some non-limiting embodiment examples, inwhich:

FIG. 1 is a perspective view with details removed for clarity of a plantaccording to the present invention;

FIG. 2 is a perspective view on an enlarged scale of a detail of FIG. 1in a different operating configuration;

FIG. 3 is a lateral view on an enlarged scale of the detail of FIG. 2;

FIG. 4 is a schematic block diagram of a control system and a drivingcontrol assembly of the plant of FIG. 1;

FIGS. 5 to 8 are experimental graphs obtained by using a prototype of aplant according to the present invention; and

FIG. 9 is a perspective view of an alternative version of the detail ofFIG. 2.

DETAILED DISCLOSURE

In accordance with a first aspect of the present invention, in FIG. 1,the number 1 indicates overall a plant for the treatment of an article2. The plant 1 comprises a robotic device 3 which, in turn, comprises aspraying head 4, which is designed to emit a jet of a substance forcovering at least a part of the surface of the article 2; a robotic arm5, which is movable with at least six degrees of freedom and on whichthe spraying head 4 is fitted; a control system 6 (FIG. 4); and adriving control assembly 7.

The control system 6 comprises a storage unit 8 and is designed tocontrol the movement of the robotic arm 5 to move the spraying head 4.In particular, the control system 6 is also designed to adjust theoperation of the spraying head 4.

The driving control assembly 7 is designed to be operated by an operator(not illustrated) to transfer movement indications for the robotic arm5. In particular, the contact unit is also designed to transfer theoperation indications for the spraying head 4.

In particular, the robotic arm 5 (FIGS. 1 and 2) comprises severalsections connected to one another in succession. Each section can berotated with respect to the preceding one around a respective rotationaxis A. The rotation around each of the axes A represents a degree offreedom of the robotic arm 5. In the embodiment illustrated, the roboticarm 5 has six degrees of freedom and, more precisely, six axes A ofrotation.

The robotic arm 5 is typically an industrial type anthropomorphic robot,for example it can be the robot GA-OL by Gaiotto Automation SpA. Therobotic arm 5 can also have more than six degrees of freedom (inparticular, more than six rotation axes A). In some cases, the degreesof freedom can be five axes of rotation and a translation (for examplehorizontal or vertical).

The driving control assembly 7 comprises a handling device 9 on which,in use, the operator exerts a force and a torque F_(c) (FIG. 4); asensor 10, which is connected to the handling device 9 and is designedto detect the force and the torque F_(s) applied to the handling device9; and a processing system 11, which is designed to provide movementindications for the robotic arm 5 as a function of the items detected bythe sensor (more precisely as a function of the force and torque F_(s)detected).

In particular, the sensor 10 has (at least) six degrees of freedom andis able to measure (at least) three forces and three torques (in aCartesian reference system). The sensor can be any known device able toperform the functions described above.

According to specific non-limiting embodiments, the sensor 10 is, forexample, the FTSens which, having measured three forces and threetorques, is able to transmit them in digital format on a CAN network.FTSens has been developed by IIT (Italian Institute of Technology) ofGenoa. In this case, the measurements are taken using strain gaugetechnology, based on the deformation of strain gauges (ofelectrical/resistance type) located inside the body of the sensor.

The FTSens sensor is provided with a DSP 16-bit microcontroller(dsPIC30F4013), able to sample up to six analog channels, and ananalog-digital converter connected to the six channels. The DSPic dealswith the synchronization and sampling, transmission of the digital datato the CAN, filtering and transformation of the signal read by thestrain gauges into forces and torques, via multiplication by thetransformation matrix characteristic of the sensor.

According to further examples, the sensor 10 is the Mini 45 by ATI,provided with force/torque sensors with 6 axes which allow measurementof all six force and torque components (Fx, Fy, Fz, Mx, My, Mz) via theuse of a transducer. The ATI sensors are provided with silicon straingauges, which provide excellent immunity to disturbances. Thecommunication interface with the sensor can be made by using one of thefollowing protocols: FTN (Ethernet, also with ProfiNet option), FTD(PCI, USB), FTS (analog voltage 0-10 V, DIO) or FTW (Wireless).

The storage unit 8 is designed to store the grobot movements made by therobotic arm 5 while the spraying head 4 is moved by the operator bymeans of the driving control assembly 7. The control system 6 isdesigned to control the movement of the robotic arm 5 as a function ofthe grobot movements stored by the storage unit 8. In particular, thecontrol system 6 is designed to control the movement of the robotic arm5 so that the robotic arm 5 (and the spraying head 4) substantiallyrepeats the grobot movements stored by the storage unit 8, morespecifically so that the spraying head 4 substantially repeats themovements carried out while the operator moves the spraying head 4.

In particular, in the present text, by “movement” or “movements” we meana path and the speed along the path. More precisely, the movement of therobotic arm 5 is the movement in space of each movable part of therobotic arm 5 in space.

In particular, the handling device 9 is fitted on the robotic arm 5(more specifically, on the sensor 10). Advantageously but notnecessarily, the handling device 9 is fitted on the robotic arm 5 in thearea of the spraying head 4, in particular in the area of an end of therobotic arm 5. More precisely, the handling device 9 is connected to therobotic arm 5 via the sensor 10 (which supports the handling device 9).According to some embodiments, the sensor 10 is fitted on the roboticarm 5.

More in particular, the sensor 10 is arranged on the robotic arm 5between the handling device 9 and the position in which the sprayinghead 4 is fitted on the robotic arm 5. In this way, the sensor 10 doesnot detect static or dynamic effects relative to the spraying head 4(and, therefore, processing of the data detected by the sensor 10 issimpler and more accurate).

In particular, the handling device 9 (more precisely the sensor 10) isfitted on the robotic arm 5 between the spraying head and the cited (atleast six) degrees of freedom.

In particular, the handling device 9 comprises at least a handgrip 12,which is designed to be grasped by the operator to move the robotic arm5 (and, therefore, the spraying head 4).

According to some non-limiting embodiments, the handling device 9comprises (at least) two handgrips 12, which are designed to be graspedby the operator to move the robotic arm 5 (and, therefore, the sprayinghead 4) and are connected to one another in an integral manner, inparticular by means of a connection element (of the handling device 9).More specifically, the connection element comprises (more precisely is)a bar transverse to the handgrips 12. In these cases, advantageously butnot necessarily, the transverse bar is fitted on the sensor 10; moreprecisely, the transverse bar is between the sensor 10 and thehandgrip/s 12.

In particular, the spraying head 4 is fitted on the robotic arm 5 bymeans of a support 4′, which projects from the robotic arm 5 (inparticular, from one end of the robotic arm 5).

According to some embodiments (like the one illustrated on pages 1 to4), the support 4′ has a first end connected to the robotic arm 5,extends (downwards) beyond the sensor 10 and has a coupling area (at asecond end opposite the first end) to which the spraying head 4 isconnected. The sensor 10 is arranged between the handling device 9 andthe first end. According to some non-limiting embodiments, the support4′ extends between the two handgrips 12. In these cases, the sprayinghead 4 is arranged between the two handgrips 12.

According to alternative embodiments (like the one in FIG. 9), thesupport 4′ extends from the robotic arm 5 substantially in a horizontaldirection.

According to some non-limiting embodiments, the driving control assembly7 (in particular, the handling device 9) comprises controls (forexample, push-buttons, levers etc.) which are designed to be operated bythe operator to adjust over time at least one operating parameter of thespraying head 10. The storage unit 8 is designed to store the adjustmentof the operating parameter (and the variation thereof in time); thecontrol system 6 is designed to adjust operation of the spraying head 4so that the adjustment of the operating parameter (and the variationthereof in time) stored is substantially repeated, in particular in amanner coordinated with the movements made by the robotic arm 5.

According to some non-limiting embodiments, the driving control assembly7 is designed to provide indications on the operating parameter (and thevariation thereof over time) to the control system 6, which is designedto operate the spraying head 4 as a function of the indications receivedfrom the driving control assembly 7.

Advantageously but not necessarily, the operating parameter is chosenfrom the group consisting of: adjustment of the flow (quantity per timeunit) of the covering substance coming out of the spraying head 4,adjustment of the degree of pulverization of the covering substancecoming out of the spraying head 4, adjustment of the width of the jet ofcovering substance coming out of the spraying head 4, adjustment of theshape of the jet of covering substance coming out of the spraying head 4(and a combination thereof).

According to some non-limiting embodiments, said operating parameter ischosen from the group consisting of: adjustment of the flow (quantityper time unit) of the covering substance coming out of the spraying head4, adjustment of the degree of pulverization of the covering substancecoming out of the spraying head 4, adjustment of the width (or shape) ofthe jet of the covering substance coming out of the spraying head 4 (anda combination thereof).

According to specific embodiments, said operating parameter is theadjustment of the flow of covering substance coming out of the sprayinghead 4. The operating parameter can also simply be activation (on) andde-activation (off) of the jet.

In some cases (and not necessarily), the driving control assembly 7 (inparticular, the handling device 9) comprises a control for enablingmovement of the robotic arm 5 (normally called “dead man” in technicaljargon) and allows stoppage of the robotic arm 5 in the event of anemergency. Typically, this command comprises a push-button which must bekept pressed by the operator until the robotic arm 5 is enabled to move.If, in use, this push-button is released or pressed for too long, thecontrol system 6 disables the possibility of movement of the robotic arm5.

According to some non-limiting embodiments, the plant 1 also comprises adevice 13 for movement of the article 2; the driving control assembly 7(in particular, the handling device 9) comprises a command (e.g. apush-button or a lever) designed to be operated by the operator tocontrol the device 13 for movement of the article 2. In these cases, thestorage unit 8 is designed to store the position (orientation) of thearticle 2 set by the operator (and the variation thereof in time). Thecontrol system 6 is designed to adjust the operation of the device 13for movement of the article 2 on the basis of the position (orientation)of the article 2 (and the variation thereof in time) stored in thestorage unit 8. More specifically, the control system 6 is designed toadjust the operation of the device 13 for movement of the article 2 soas to repeat the position (orientation) of the article 2 (and thevariation thereof in time) stored in the storage unit 8.

According to some non-limiting embodiments (like the one illustrated),the device 13 comprises a rotating platform 13′ on which, in use, thearticle 2 is arranged. In particular, the platform 13′ rotates around avertical axis (not illustrated).

Advantageously but not necessarily, the processing system 11 is designedto estimate a non-contact force and torque F_(nc) as a function ofstatic and dynamic components resulting from the load (in particular,the handling device 9) of what is fitted on (more precisely, supportedby) the sensor 10 (more precisely, a sensitive part of the sensor 10)and is designed to obtain an estimated force and torque F*_(c) (of whatis applied by the operator on the handling device 9) as a function ofthe force and torque F_(s) detected (sum of F*_(c) and F_(nc)) and ofthe estimated non-contact force and torque F_(nc). In these cases, theprocessing system 11 is designed to provide movement indications for therobotic arm 5 as a function of the force and torque F*_(c) estimated bythe processing system 11. In particular, the force and torque F*_(c) areestimated by subtracting the non-contact force and torque F_(nc) fromthe detected force and torque F_(s).

In particular, it should be noted that all the forces and torquesindicated above (F_(nc), F*_(c), F_(c) and F_(s)) have components in thethree dimensions of Cartesian space.

According to some non-limiting embodiments, the static and dynamiccomponents resulting from the load comprise gravity and inertial andCoriolis forces. In particular, the static components comprise thegravity. In particular, the dynamic components are estimated (at leastpartly) as a function of the angular speed ω, angular acceleration α,linear acceleration a and inertia (in particular, of the handling device9) of what is fitted on (more precisely, supported by) the sensor 10.

Advantageously but not necessarily, the processing system 11 comprises aprocessing unit 14, which is designed to estimate (calculate) theangular speed ω, the angular acceleration α and the linear accelerationa as a function of the Xrobot application (i.e. the configuration foreach axis of rotation A) of the robotic arm 5. According to somespecific non-limiting embodiments, the processing unit 14 comprises (inparticular is) a Kalman filter.

These parameters can be obtained directly from the encoders present onthe robotic arm, or via additional accelerometers positioned on therobotic arm 5. Experimental results show that the measurements obtainedfrom the encoders are more accurate.

According to some non-limiting embodiments, the processing system 11also comprises a compensation unit 15 which is designed to estimate theforce and the torque F*_(c) as described above. In particular, thecompensation unit 15 is connected to the processing unit 14 and isdesigned to receive from it the angular speed ω, the angularacceleration α and the linear acceleration a.

Advantageously but not necessarily, the processing system 11 alsocomprises a control system 16, which is designed to calculate areference position X_(ref) (the position of the movable end of therobotic arm 5, on said end of which, in particular, the driving controlassembly 7 is fitted) as a function of the force and torque F*_(c)(received from the compensation unit 15).

In some non-limiting cases, the control system 16 comprises (is) anadmittance control or an impedance control. Advantageously but notnecessarily, the control system 16 comprises (is) an admittance control.The admittance control provides a high level of accuracy in thenon-contact tasks.

In particular, in a specific configuration thereof, the admittancecontrol causes the robot to interact with the environment according to amass damping system characterized by the following equation:M _(d) {umlaut over (x)}+D _(d) {umlaut over (x)}=F _(s)  (A)in which M_(d) andD_(d) are the matrix of the desired inertia anddamping, {umlaut over (x)} is the Cartesian speed and {umlaut over (x)}is the Cartesian acceleration.

However, as known in the literature, since interaction with the user canlead to instability, the admittance control parameters areadvantageously but not necessarily varied and therefore the inertia anddamping are variable in time and not constant. The variable admittancemodel is, according to some non-limiting embodiments, the following:M _(d)(t){umlaut over (x)}+D _(d)(t){umlaut over (x)}=F _(s)  (B)

According to some non-limiting embodiments, the control system 6comprises inverse kinematics 17, which is designed to determine theposition (movements) q_(ref) for each degree of freedom to reproduce thereference position X_(ref) (which, in use, is provided by the processingsystem 11—in particular, by the control system 16—to the control system6—in particular, to the inverse kinematics 17). More precisely, thecontrol system 6 (in particular, the inverse kinematics 17) is designedto determine the angular position (of each section) around each axis A.

In particular, the control system 6 also comprises a position control 18which is designed to provide the actuation torque to move the roboticarm 5 in the desired position (in other words, to reproduce thereference position X_(ref)). More precisely, the position control 18operates on the basis of the position q_(ref) provided by the inversekinematics 17.

Note that, according to different embodiments, the various components ofthe processing system 11 (the processing unit 14, the compensation unit15, the control system 16) and the different components of the controlsystem 6 (inverse kinematics 17, position control 18) can be understoodas physical devices or as parts of a software system that operate asdescribed above.

For the sole purpose of making operation of the plant 1 morecomprehensible, some operating phases are summarized below. The sensor10 measures the force and the torque F_(s), composed of the forceactually exerted by the operator (contact force and torque F_(c)) and bythe static and dynamic components resulting from the load (non-contactforces and torques F_(nc)). F_(s) is transmitted to the loadcompensation unit 15, which performs an estimate of the non-contactforces and torques F_(nc) (weight force, inertial, gravitational andCoriolis forces) and obtains an estimate of the force exerted by theoperator (F*_(c)). The angular speed ω, the linear acceleration a andthe angular acceleration α provided by the processing unit 14 (Kalmanfilter) and calculated on the basis of the robot position are used,together with the load inertia matrix (based also on the coordinates ofthe centre of mass), for estimate of the forces and torques F_(nc). Thecontact force F*_(c) enters the control system 16 (admittance control),which calculates the reference position X_(ref) for the position control18. Since the position is expressed in Cartesian space, it is expedientfor the inverse kinematics 17 to calculate the corresponding angularposition around the axes A. Lastly, the position control 18 provides theactuation torque to the joints to move the robotic arm 5 to the desiredreference position X_(ref). To program the system in a complete manner,it is advantageous for the angular positions around each axis A to berecorded by the storage unit 8 during execution of the trajectory,together with the painting data.

Some aspects of the operation of the plant 1 will be explained infurther detail with reference to a second aspect of the presentinvention described below.

According to some non-limiting embodiments, the plant 1 (in particular,the robotic device 3) is designed to implement the method as per thesecond aspect of the present invention.

In accordance with to the second aspect of the present invention, amethod is provided for the surface treatment of an article 2 by means ofa robotic device 3, which performs the same functions and comprises thesame components as the robotic device 3 described in the ambit of thefirst aspect of the present invention. More precisely, the roboticdevice 3 is like the one described according to the first aspect of thepresent invention. In particular, the robotic device 3 is part of theplant 1 of the first aspect of the present invention.

The method comprises a learning step, during which the operator movesthe spraying head 4 by means of the driving control assembly 7 and themovements made by the spraying head 4 are stored by the storage unit 8;and a reproduction step, which is subsequent to the learning step andduring which the control system 6 operates the robotic arm 5 so that thespraying head 4 substantially repeats the movements stored by thestorage unit 8 (in particular, carried out during the learning step).

During the learning step, the operator exerts a force and a torque onthe handling device 9; the sensor 10 detects the force and torqueapplied to the handling device 9; and the processing system 11 (inparticular, using the Kalman filter) provides movement indications forthe robotic arm 5 as a function of the items detected by the sensor 10.In particular, during the learning step, the operator grasps thehandling device 9.

In particular, the Kalman filter is used during the learning step.

More precisely, the Kalman filter is used at the input (to theprocessing system 11) to filter (all the) stochastic noises generated bythe movements of the operator (which are not always precise).

Additionally or alternatively, the Kalman filter is (also) used duringthe reproduction step. For example, in this regard if, in use, an objectknocks against the robot, the Kalman filter by-passes the impact read onthe encoders and continues its movement normally.

Advantageously but not necessarily, during the learning step, theprocessing system 11 estimates a non-contact force and torque F_(nc) asa function of static and dynamic components resulting from the load (inparticular, of the handling device) of what is fitted on (moreprecisely, supported by) the sensor 10 (more precisely, on a sensitivepart of the sensor 10) and obtains the estimated force and torque F*_(c)(applied by the operator on the handling device 9) as a function of theforce and torque F_(s) detected and the estimated non-contact force andtorque F_(nc). In these cases, the processing system 11 providesmovement indications for the robotic arm 5 as a function of the forceand torque F*_(c) estimated and provided by the processing system 11. Inparticular, the force and torque F*_(c) are estimated by subtracting thenon-contact force and torque F_(nc) from the detected force and torqueF_(s).

According to some non-limiting embodiments, the static and dynamiccomponents resulting from the load comprise gravity and inertial andCoriolis forces. In particular, the dynamic components are estimated asa function of the angular speed ω, angular acceleration α, linearacceleration a and inertia (inertia tensor) of what is fitted on (moreprecisely, supported by) the sensor 10 (more precisely, on a sensitivepart of the sensor 10).

In particular, the inertia, more precisely the inertia tensor, is amatrix. More specifically, the matrix is

$\begin{matrix}{s_{I} = {\begin{bmatrix}s_{I_{xx}} & s_{I_{xy}} & s_{I_{xz}} \\s_{I_{xy}} & s_{I_{yy}} & s_{I_{yz}} \\s_{I_{xz}} & s_{I_{yz}} & s_{I_{zz}}\end{bmatrix}.}} & (1)\end{matrix}$

Such a matrix is present in the Newton-Euler equations on the movementof a rigid body subject to external forces:^(S) f=m ^(S) a−m ^(S) g+ ^(S) α×m ^(S) c+ ^(S)ω×(^(S) ω×m ^(S) c)^(S)τ=^(S) I ^(S)α+^(S)ω×(^(S) I ^(S)ω)+m ^(S) c× ^(S) a−m ^(S) c× ^(S)g  (2)and to obtain it, the Huygens-Steiner theorem must be applied, addingthe contribution relative to translation of the rotation axes to theinertia tensor referring to the centre of gravity ^(G)I (BrunoSiciliano, Lorenzo Sciavicco, Luigi Villani, and Giuseppe Oriolo.Robotics: modelling, planning and control. Springer Science & BusinessMedia, 2010″)^(S) I= ^(G) I+mS ^(T) S  (3).

The matrix operator S(·) is defined as:

$\begin{matrix}{S = \begin{bmatrix}0 & {- c_{z}} & c_{y} \\c_{z} & 0 & {- c_{x}} \\{- c_{y}} & c_{x} & 0\end{bmatrix}} & (4)\end{matrix}$wherein the components of the vector c represent the distance betweenthe centre of mass of the object and the origin of the reference systemof the sensor 10.

The forces and torques measured ^(S)f, ^(S)τ (corresponding to F_(s)),the linear acceleration vectors ^(S) _(α) (above and in FIG. 4 indicatedas α) and angular acceleration vectors ^(S) _(α)(above and in FIG. 4indicated as α), the angular speed vector ^(S)ω (above and in FIG. 4indicated as ω), the gravity vector ^(S) _(g), the coordinates of thecentre of mass ^(S) _(C) and the inertia matrix ^(S) _(I) are expressedin the reference system S of the sensor 10.

The equations 2 can be rewritten as:

$\begin{matrix}{{\begin{bmatrix}{\,^{s}f} \\{\,^{s}\tau}\end{bmatrix} = {{{\,^{s}V}\left( {{\,^{s}a},{\,^{s}\alpha},{\,^{s}\omega},{\,^{s}{\mathcal{g}}}} \right)}{\,^{s}\varphi}}}{Wherein}} & (5) \\{{\,^{s}V} = \left\lbrack {\begin{matrix}{a_{x} - {\mathcal{g}}_{x}} & {{- \omega_{y}^{2}} - \omega_{z}^{2}} & {{\omega_{x}\omega_{y}} - \alpha_{z}} & {{\omega_{x}\omega_{z}} + \alpha_{y}} & 0 \\{a_{y} - {\mathcal{g}}_{y}} & {{\omega_{x}\omega_{y}} + \alpha_{z}} & {{- \omega_{x}^{2}} - \omega_{z}^{2}} & {{\omega_{y}\omega_{z}} - \alpha_{x}} & 0 \\{a_{z} - {\mathcal{g}}_{z}} & {{\omega_{x}\omega_{z}} - \alpha_{y}} & {{\omega_{y}\omega_{z}} + \alpha_{x}} & {{- \omega_{y}^{2}} - \omega_{x}^{2}} & 0 \\0 & 0 & {a_{z} - {\mathcal{g}}_{z}} & {{\mathcal{g}}_{y} - a_{x}} & \alpha_{x} \\0 & {{\mathcal{g}}_{z} - a_{z}} & 0 & {a_{x} - {\mathcal{g}}_{x}} & {\omega_{x}\omega_{z}} \\0 & {a_{y} - {\mathcal{g}}_{y}} & {{\mathcal{g}}_{x} - a_{x}} & 0 & {{- \omega_{x}}\omega_{y}}\end{matrix}\begin{matrix}0 & 0 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & 0 \\{\alpha_{y} - {\omega_{x}\omega_{z}}} & {\alpha_{z} + {\omega_{x}\omega_{z}}} & {{- \omega_{y}}\omega_{z}} & {\omega_{y}^{2} - \omega_{z}^{2}} & {\omega_{y}\omega_{z}} \\{\alpha_{x} + {\omega_{y}\omega_{z}}} & {\omega_{z}^{2} - \omega_{x}^{2}} & \alpha_{y} & {\alpha_{z} - {\omega_{x}\omega_{y}}} & {{- \omega_{x}}\omega_{z}} \\{\omega_{x}^{2} - \omega_{y}^{2}} & {\alpha_{x} - {\omega_{y}\omega_{z}}} & {\omega_{x}\omega_{y}} & {\alpha_{y} + {\omega_{x}\omega_{z}}} & \alpha_{z}\end{matrix}} \right\rbrack} & (6)\end{matrix}$

The vector ^(S)φ contains the complete set of inertia parameters of theload:^(S)φ=[m, ^(S) c _(x) ,m ^(S) c _(y) ,m ^(S) c _(z),^(S) I _(xx),^(S) I_(xy),^(S) I _(xz),^(S) I _(yy),^(S) I _(yz,) ^(S) I _(zz)]^(T)  (7)

Once the elements of the vector ^(S)φ, i.e. the mass of the load m, theposition of the centre of mass ^(S)c=[^(S)c_(x); ^(S)c_(y); ^(S)c_(z)],the inertia tensor ^(S)I and the matrix ^(S)V are known, the non-contactforce and torsional moment F_(nc) is obtained from the equations (2) asfollows:

$\begin{matrix}{\begin{bmatrix}{{}_{}^{}{}_{}^{}} \\{{}_{}^{}{}_{}^{}}\end{bmatrix} = {{{\,^{s}V}\left( {{\,^{s}a},{\,^{s}\alpha},{\,^{s}\omega},{\,^{s}{\mathcal{g}}}} \right)}{\,^{s}\varphi}}} & (8)\end{matrix}$

The contribution resulting from the load dynamics is then subtractedfrom the measurement of the sensor 10, thus obtaining an estimate of theeffective force and moment of contact F_(c). This value is then enteredin the admittance control to obtain the reference application X_(ref)used by the control system 6 to provide the desired dynamics.

The matrix ^(S)V does not take account of the thermal drift and theoffset of the sensor 10. Two strategies, for example, are possible tocompensate this effect: either the values measured are re-setconsidering the orientation of the sensor and of the associated frame,or the offset can be estimated directly by increasing the number ofparameters of the matrix ^(S)φ. Advantageously but not necessarily, thefirst method is implemented by performing a calibration every time thethermal drift significantly alters the force recorded by the sensor. Thecalibration operation is integrated in the robotic device 3.

To perform the calibration without having to remove the load every time,the terms relative to the offset are calculated considering the mass andorientation of what is fitted on the sensor 10. A pseudo-gravitationalterm is constructed which takes account of these factors:

$\begin{matrix}{F_{{\mathcal{g}}_{{ini}t}} = {{{\,^{s}V}\left( {0,0,0,{{}_{}^{}{}_{}^{}}} \right)}{\,^{s}\varphi}}} & (9) \\{\begin{bmatrix}f_{g_{init}} \\\tau_{g_{init}}\end{bmatrix} = \begin{bmatrix}{m\mspace{11mu}{{}_{}^{}{}_{}^{}}} \\{m\mspace{11mu}{{}_{}^{}{}_{}^{}}} \\{m\mspace{11mu}{{}_{}^{}{}_{}^{}}} \\{{m\mspace{11mu}{{}_{}^{}{}_{}^{}}{{}_{}^{}{}_{}^{}}} - {m\mspace{11mu}{{}_{}^{}{}_{}^{}}{{}_{}^{}{}_{}^{}}}} \\{{{- m}\mspace{11mu}{{}_{}^{}{}_{}^{}}{{}_{}^{}{}_{}^{}}} + {m\mspace{11mu}{{}_{}^{}{}_{}^{}}{{}_{}^{}{}_{}^{}}}} \\{{m\mspace{11mu}{{}_{}^{}{}_{}^{}}{{}_{}^{}{}_{}^{}}} - {m\mspace{11mu}{{}_{}^{}{}_{}^{}}{{}_{}^{}{}_{}^{}}}}\end{bmatrix}} & (10)\end{matrix}$

Since the mass and inertia values of the load which are inserted in thevector ^(S)φ are not precise, it is expedient to consider them asestimates subject to uncertainty on the parameters (i.e. ^(S){circumflexover (φ)}=^(S)φ±Δ^(S)φ^(e)) and to an error deriving from the processingunit 14. The contact forces/torques F_(c) can therefore be re-written asfollows:F _(c) =F _(s) −F _(nc) +F _(ginit)  (11)

The simplest way of managing these uncertainties is to apply athreshold: if the estimate is below a fixed value, it must be consideredzero. The limit of this method is the need to find the right compromisebetween sensitivity and incorrect detection of the contact force. Thesolution is to use an adaptive threshold, exploiting the linearity ofthe equation 8:F _(th)=|^(S) V(^(S)α,^(S)α,^(S)ω,^(S) g)Δφ|+F _(min)  (12)where F_(min) represents a fixed safety margin.

A further aspect to be advantageously (but not necessarily) consideredfor detecting the contact force is the spectral content of the signal.

Some studies show that intentional human inputs have a dominantfrequency in the band from 0 to 5 Hz, whereas accidental impacts areusually represented by peaks at high frequencies (greater than 10 Hz).Since the objective is to exploit the former to provide an input to thecontrol system 16, a low-pass filter is used on the output of theequation 11, obtaining a filtered contact force and torsional momentF_(cf) which takes account of the intentional movements of the operator,eliminating the accidental impacts.

The resulting force and torsional moment after application of theadaptive threshold and low-pass filter are (therefore) as follows:

$\begin{matrix}{{\hat{F}}_{c_{h}}^{i} = \left\{ \begin{matrix}{{\hat{F}}_{c_{f}}^{i} - F_{th}^{i}} & {{{if}\mspace{14mu}{\hat{F}}_{c_{f}}^{i}} > F_{th}^{i}} \\{{\hat{F}}_{c_{f}}^{i} + F_{th}^{i}} & {{{if}\mspace{14mu}{\hat{F}}_{c_{f}}^{i}} < {- F_{th}^{i}}} \\0 & {otherwise}\end{matrix} \right.} & (13)\end{matrix}$wherein F^(i) is the i-th component of a vector with 6 degrees offreedom containing forces and torsional moments (i.e. F¹=f_(x),F⁴=τ_(x)).

During the man-robot interaction it is necessary to guarantee stabilityto make the system safe and minimize the physical force of the operator.For this purpose, the admittance control is used and the choice of therelative parameters is of the utmost importance. What is proposed hereallows identification of deviations from the nominal behaviour of arobot controlled in admittance, adapting the controller parameters so asto guarantee the passivity thereof.

The choice of the parameters influences the way in which the robotinteracts with the operator. For example, if the operation requires finemovements, the inertia and the damping will have high values to make therobot less reactive and obtain a more fluid movement. On the other hand,if the operation requires high speeds and accelerations, the parameterswill have lower values. Furthermore, also the rigidity which theoperator exerts during the interaction with the robot influences thebehaviour of the system. In particular, the more rigid the operator, thefarther the system moves from the ideal behaviour defined by theequation (B), vibrating and making the interaction difficult and unsafe.For this reason, deviations from the ideal behaviour must first beidentified and then cancelled (or reduced), restoring the stability ofthe system.

What is herein proposed allows adaptation of the admittance controlparameters online, during interaction between the operator and therobot. Initially a heuristic is defined to recognize the deviations ofthe robot from the nominal behaviour; subsequently a method is presentedfor adaptation of the parameters which guarantees reset of the nominalconditions, without excessively increasing the physical effort of theoperator. The passivity and therefore the stability of the robotcontrolled in admittance is guaranteed. A less conservative solution isproposed which entails the use of virtual energy tanks, which store theenergy dissipated by the system in order to subsequently re-use it.

According to some non-limiting embodiments, the inertia and dampingparameters are varied (adapted) when the following inequality is notverified:ψ({dot over (x)},{umlaut over (x)},F _(s))=∥F _(s) −M _(d) {umlaut over(x)}−D _(d) {umlaut over (x)}∥≤ε  (14)in which ε>0 is a minimum threshold obtained experimentally. As alreadyindicated above, M_(d) andD_(d) are the desired inertia and dampingmatrix, k is the Cartesian speed and {umlaut over (x)} is the Cartesianacceleration.

Considering the dynamic behaviour of the admittance control, thebehaviour of the robot when the inequality (14) is valid is defined as“nominal behaviour”.

Using this equation, it is possible to define a heuristic foridentification of the deviation from the nominal behaviour which occurswhen, for example, the operator stiffens his arm during interaction withthe robot.

Once this deviation has been identified, the admittance controlparameters must be adapted. Via use of the energy tanks it is possibleto define the inertia increment required to re-set the system to thenominal conditions, guaranteeing the passivity thereof.

Advantageously but not necessarily (during the learning step), theadmittance control (of the control system 16) is varied (adapted) as afunction of the detected force and torque F_(s). In particular, theadmittance control parameters are varied (adapted). More specifically,the inertia and damping parameters of the admittance control are varied(adapted).

According to some non-limiting embodiments, the admittance control (ofthe control system 16) is varied (adapted) by modifying (adapting) theparameters of the admittance control. More specifically, the inertia anddamping parameters of the admittance control are varied (adapted).

According to some non-limiting embodiments, the inertia is varied by (asa function of) the following equation:½λ_(M) ∥{umlaut over (x)} _(M)∥²(t _(f) −t _(i))≤T(t _(i))−δ  (15)wherein λ_(M) is the maximum eigenvalue of the derivative of the inertiamatrix {dot over (M)}_(d)(t) in the time interval in which theparameters

$\left( {\lambda_{M} = {\begin{matrix}\max & \max \\{t \in \left\lbrack {t_{i},t_{f}} \right\rbrack} & {{j = 1},\ldots\mspace{14mu},n}\end{matrix}{\lambda_{j}\left( {{\overset{.}{M}}_{d}(t)} \right)}}} \right)$vary; ∥{umlaut over (x)}_(M)∥² is the squared norm of the maximumCartesian speed; (t_(f)−t_(i)) is the time interval in which thevariation takes place; T(t_(i)) is the energy stored in the tank at thetime considered; δ is the minimum energy that must be present in thetank.

Let's assume that the desired inertia matrix and damping matrix arediagonal matrixes, as in common practice, defined according to theequations (16) and (17)M _(d)(t)=diag{m ₁(t), . . . ,m _(n)(t)}  (16)D _(d)(t)=diag{d ₁(t), . . . ,d _(n)(t)}  (17)

Since M_(d)(t) is diagonal, also {dot over (M)}_(d)(t) is diagonal andits eigenvalues are the elements on the main diagonal.

Consequently the inequality (15) can be re-written as (18)

$\begin{matrix}{{{{{\overset{.}{m}}_{j}(t)} \leq {\frac{2\left( {{T\left( t_{i} \right)} - \delta} \right)}{{{\overset{.}{x}}_{M}}^{2}\left( {t_{f} - t_{i}} \right)}\mspace{20mu}{\forall j}}} = 1},\ldots\mspace{14mu},{n.}} & (18)\end{matrix}$

By calculating the integral of the inequality (18), the equation (19) isobtained.

According to some non-limiting embodiments, the inertia variation iscalculated on the basis of (using) the equation (17):

$\begin{matrix}{{{M_{d}\left( t_{f} \right)} - {M_{d}\left( t_{i} \right)}} = \frac{2\left( {{T\left( t_{i} \right)} - \delta} \right)}{{{\overset{.}{x}}_{M}}^{2}}} & (19)\end{matrix}$wherein M_(d)(t_(f)) and M_(d)(t_(i)) are the inertias at the initialand final times of the variation interval.

The equation (17) represents the maximum inertia variation admitted, onthe basis of the energy available at time t_(i). In practice, this valuecould be very high: consequently, the direct application of (19) couldentail excessive inertia variations. For this reason, in some cases anupper limit (ΔM) is used, experimentally defined, to the permittedinertia variation, on the basis of the following inequality (20):M _(d)(t _(f))−M _(d)(t _(i))≤ΔM  (20).

Advantageously, but not necessarily, the inertia variation is calculatedon the basis of (using) the equations (19) and (20), in whichM_(d)(t_(f)) and M_(d)(t_(i)) are the inertias at the initial and finaltimes of the variation interval.

In particular, the damping is varied so as to maintain the ratio betweeninertia and damping substantially constant. This allows the systemdynamics to be maintained similar to those prior to the variation, whichis more intuitive for the operator.

According to some non-limiting embodiments, during the learning step,the operator adjusts over time at least one operating parameter of thespraying head, and the applied operating parameter (and variationthereof in time) is substantially stored by the storage unit 8. In thesecases, during the reproduction step, the control system 6 adjustsoperation of the spraying head 4 so that the operating parameter storedduring the learning step (and variation thereof in time) issubstantially repeated. Advantageously but not necessarily, during thereproduction step, the control system 6 adjusts the operation of thespraying head 4 so that the operating parameter stored during thelearning step (and variation thereof over time) is substantiallyrepeated, in particular in a manner coordinated with the movements madeby the spraying head 4.

Advantageously but not necessarily, the operating parameter is chosenfrom the group consisting of: adjustment of the flow (quantity per timeunit) of the covering substance coming out of the spraying head 4,adjustment of the degree of pulverization of the covering substancecoming out of the spraying head 4, adjustment of the width of the jet ofcovering substance coming out of the spraying head, adjustment of theshape of the jet of covering substance coming out of the spraying head 4(and a combination thereof).

According to some non-limiting embodiments, said operating parameter ischosen from the group consisting of: adjustment of the flow (quantityper time unit) of the covering substance coming out of the spraying head4, adjustment of the degree of pulverization of the covering substancecoming out of the spraying head 4, adjustment of the width (or shape) ofthe jet of covering substance coming out of the spraying head 4 (and acombination thereof).

In some specific cases, the operating parameter comprises (is)adjustment of the flow (quantity per time unit) of the coveringsubstance coming out of the spraying head 4.

According to some non-limiting embodiments, during the learning step,the operator adjusts in time at least one operating parameter of thespraying head 4 by acting on the driving control assembly 7, whichprovides indications on the operating parameter to the control system 6;the control system 6 operates the spraying head 4 as a function of theindications received from the driving control assembly 7.

Advantageously but not necessarily, during the learning step, theoperator moves (in particular, adjusts over time the orientation of) thearticle 2 and the position is thus obtained (in particular, theorientation obtained and the variation thereof in time) is stored by thestorage unit. In these cases, during the reproduction step, the controlsystem 6 adjusts the position (orientation) of the article 2 so that theposition (orientation) of the article 2 stored during the learning step(and variation thereof in time) is substantially repeated, in particularin a manner coordinated with the movements made by the spraying head 4.

According to some non-limiting embodiments, during the learning step,the driving control assembly 7 provides movement indications to thecontrol system 6, which in turn operates the robotic arm 5 as a functionof the indications received from the driving control assembly 7.

Advantageously but not necessarily, the handling device 9 comprises atleast one handgrip 12 which, during the learning step, is grasped by theoperator to move the spraying head 4.

In particular, the handling device 9 comprises at least two handgrips 12which, during the learning step, are grasped by the operator to move thespraying head 4 and are connected to each other in an integral manner,in particular by means of a connection element of the handling device.

According to some embodiments, the article 2 is a ceramic article, inparticular a sanitary article, for example a washbasin and/or a sinkand/or console and/or shower tray.

Further characteristics of the present invention will become clear fromthe following description of a merely illustrative and non-limitingexample.

A prototype of the plant 1 is provided according to some embodiments ofthe invention. In particular, the force and the torque F_(s) weremeasured and the forces and torques F_(nc) and F_(c) were estimated asdescribed above.

The results obtained are shown in FIGS. 5 to 7. FIGS. 5 a), b) and c)illustrate the force detected F_(s) in the direction x, y and zrespectively. FIGS. 5 d), e) and f) illustrate the torque detected inthe direction x, y and z respectively. FIGS. 6 a), b) and c) illustratethe estimated force exerted by the operator in the direction x, y and zrespectively. FIGS. 6 d), e) and f) illustrate the estimated torqueexerted by the operator in the direction x, y and z respectively. FIGS.7 a), b) and c) illustrate the estimated non-contact force in thedirection x, y and z respectively. FIGS. 7 d), e) and f) illustrate theestimated non-contact torque in the direction x, y and z respectively.

The illustrations of FIG. 5 to 7 show that a surprisingly goodcompensation was obtained. In particular, comparing FIGS. 6 and 7 withFIG. 5 it can be noted that the compensation is particularly efficient,in fact the forces and torques are more fluid.

FIGS. 8 a), c) and e) show the trajectories in the directions x, y and zrespectively, followed during the learning step (broken lines) andduring the reproduction step (continuous lines). FIGS. 9 a), c) and e)show the differences between the trajectories in the directions x, y andz respectively, followed during the learning step and during thereproduction step. The plant 1 and the method according to the presentinvention are extremely precise.

The invention claimed is:
 1. A method for the surface treatment of anarticle by means of a robotic device; the robotic device comprising aspraying head, which is designed to emit a jet of a covering substancefor covering at least part of the surface of the article; a robotic arm,which is movable with at least six degrees of freedom and on which thespraying head is fitted; a control system, which comprises a storageunit and is designed to control the movement of the robotic arm so as tomove the spraying head in space; a driving control assembly, which isdesigned to be operated by an operator so as to transfer movementindications for the robotic arm; the driving control assembly comprisesa handling device; a sensor, which is connected to the handling device;and a processing system; the handling device is fitted on the roboticarm in the area of the spraying head; the handling device is connectedto the robotic arm through said sensor, which is fitted on the roboticarm; the method comprising: a learning step, during which the operatormoves the spraying head by means of the driving control assembly and themovements made by the spraying head are stored in the storage unit; anda reproduction step, which takes place after the learning step andduring which the control system operates the robotic arm so that thespraying head substantially repeats the movements stored by the storageunit; wherein during the learning step, the operator exerts a force anda torque (F_(c)) upon the handling device; the sensor detects a forceand a torque (F_(s)) applied to the handling device; and the processingsystem provides movement indications for the robotic arm as a functionof the items detected by the sensor; and wherein during the learningstep, an admittance control is varied as a function of the detectedforce and torque (Fs) and inertia and damping parameters of theadmittance control are varied as a function of the detected force andtorque (Fs).
 2. The method according to claim 1, wherein, during thelearning step, the processing system estimates a non-contact force andtorque (F_(nc)) as a function of static and dynamic components resultingfrom the load of what is fitted on the sensor and obtains an estimatedforce and torque (F*_(c)) applied by the operator to the handling deviceas a function of the detected force and torque (F_(s)) and on theestimated non-contact force and torque (F_(nc)); the processing systemprovides movement indications for the robotic arm as a function of theestimated force and torque (F*_(c)) provided by the processing system.3. The method according to claim 2, wherein the static componentscomprise gravity; the dynamic components are estimated as a function ofan angular speed ω, an angular acceleration α, an linear acceleration αand an inertia of what is fitted on the sensor.
 4. The method accordingto claim 1, wherein the control system is also designed to adjustoperation of the spraying head.
 5. The method according to claim 1,wherein the processing system comprises a processing unit, and theprocessing unit comprises a Kalman filter.
 6. The method according toclaim 1, wherein the handling device is fitted on the robotic arm at anend of the robotic arm; wherein, the sensor is arranged on the roboticarm between the handling device and the position in which the sprayinghead is fitted on the robotic arm.
 7. The method according to claim 1,wherein, during the learning step, the operator adjusts in time at leastone operating parameter of the spraying head and the applied operatingparameter is substantially stored by the storage unit; during thereproduction step, the control system adjusts the operation of thespraying head so that the operating parameter stored during the learningstep is substantially repeated so as to be substantially coordinatedwith the movements made by the spraying head.
 8. The method according toclaim 7, wherein said operating parameter is chosen from the groupconsisting of: adjustment of the flow (quantity per time unit) of thecovering substance coming out of the spraying head, adjustment of thedegree of pulverization of the covering substance coming out of thespraying head, adjustment of the width of the jet of covering substancecoming out of the spraying head; adjustment of the shape of the jet ofcovering substance coming out of the spraying head, and a combinationthereof.
 9. The method according to claim 1, wherein, during thelearning step, the operator adjusts in time at least one operatingparameter of the spraying head by acting upon the driving controlassembly, which provides the control system with indications on theoperating parameter; the control system operates the spraying head as afunction of the indication received from the driving control assembly.10. The method according to claim 1, wherein, during the learning step,the operator adjusts in time the orientation of the article and theapplied orientation is substantially stored by the storage unit; duringthe reproduction step, the control system adjusts the orientation of thearticle so that the orientation of the article stored during thelearning step is substantially repeated so as to be coordinated with themovements made by the spraying head.
 11. The method according to claim1, wherein, during the learning step, the driving control assemblyprovides the control system with movement indications and, in turn, thelatter operates the robotic arm as a function of the indicationsreceived from the driving control assembly.
 12. A plant for the surfacetreatment of an article, the plant comprising: a robotic device, whichcomprises: a spraying head, which is designed to emit a jet of acovering substance for covering at least part of the surface of thearticle; a robotic arm, which is movable with at least six degrees offreedom and on which the spraying head is fitted; a control system,which comprises a storage unit and is designed to control the movementof the robotic arm so as to move the spraying head; and a drivingcontrol assembly, which is designed to be operated by an operator so asto transfer movement indications for the robotic arm; wherein thedriving control assembly comprises a handling device, upon which, inuse, the operator exerts a force and a torque (F_(c)); a sensor, whichis connected to the handling device and is designed to detect a forceand a torque (F_(s)) applied to the handling device; and a processingsystem, which is designed to provide movement indications for therobotic arm as a function of the items detected by the sensor; whereinthe storage unit is designed to store the movements made by the roboticarm while the spraying head is moved by the operator by means of thedriving control assembly; and wherein the control system is designed tocontrol the movement of the spraying head as a function of the movementsstored by the storage unit; and wherein the control system comprises anadmittance control, which is varied as a function of the detected forceand torque (F_(s)), and inertia and damping parameters of the admittancecontrol are varied as a function of the detected force and torque (Fs).13. The plant according to claim 12, wherein the handling device isfitted on the robotic arm at the spraying head and is connected to therobotic arm through said sensor; wherein, the handling device is fittedon the robotic arm at an end of the robotic arm and the sensor isarranged on the robotic arm between the handling device and the positionin which the spraying head is fitted on the robotic arm.
 14. The plantaccording to claim 12, wherein the handling device comprises at leastone handgrip, which is designed to be grasped by the operator in orderto move the spraying head.
 15. The plant according to claim 12, whereinthe handling device comprises at least two handgrips, which are designedto be grasped by the operator in order to move the spraying head and areconnected to one another in an integral manner by means of a connectionelement of the handling device.
 16. The plant according to claim 12,wherein the driving control assembly comprises commands, which aredesigned to be operated by the operator in order to adjust in time atleast one operating parameter of the spraying head; wherein the storageunit is designed to store the adjustment of the operating parameter; thecontrol system being designed to adjust the operation of the sprayinghead so that the adjustment of the operating parameter is substantiallyrepeated so as to be coordinated with the movements made by the roboticarm.
 17. The plant according to claim 12 and comprising: a device formoving the article; the driving control assembly comprises a command,which is designed to be operated by the operator in order to control thedevice for moving the article; the storage unit being designed to storethe position of the article set by the operator; the control systembeing designed to adjust the operation of the device for moving thearticle based on the position of the article stored in the storage unit.18. The plant according to claim 12, wherein the processing system isdesigned to estimate a non-contact force and torque (F_(nc)) as afunction of static and dynamic components resulting from the load ofwhat is fitted on the sensor and is designed to obtain an estimatedforce and torque (F*_(c)) as a function of the detected force and torque(F_(s)) and on the estimated non-contact force and torque (F_(nc));wherein the processing system is designed to provide movementindications for the robotic arm as a function of the force and torque(F*_(c)) estimated by the processing system; and wherein the dynamiccomponents are estimated as a function of an angular speed ω, an angularacceleration α, a linear acceleration α and an inertia of what is fittedon the sensor.